Photodynamic therapy (PDT) is a minimally invasive cancer treatment and has been used in clinic to improve cancer patients' quality of life and survival time. The lack of specific delivery of the photosensitizers, however, is a significant limitation of PDT. Non-targeted, conventional photodynamic therapy cannot deliver the photosensitizers specifically to the tumor and the photosensitizers often circulate in the body long after treatment and cause sensitivity to light for several months.